This invention relates to improvements in the automatic bleed unit for a disposable filter fully described in PCT/IB00/01527 Published as WO01/33069 A1 in the name of the same Applicant, the text of which is to be considered an integral part of the present description for suitable reference.
Essentially, the device of said document comprises a sensor means associated with the chamber of the filter for the vehicle fuel (such as diesel oil) in which the water present in said fuel accumulates, a withdrawal device provided for discharging said water when it reaches a predetermined maximum level, and a microprocessor (or electronic card) which is connected to said sensor means and to said withdrawal device such as to activate this latter, with the vehicle engine at rest and the relative electrical system live, when the water reaches said predetermined maximum level.
In particular with said vehicle electrical system there is associated a visual indicator which is activated by the sensor means via the microprocessor, the said microprocessor being arranged to maintain the withdrawal device deactivated when the vehicle engine rotates and said visual indicator is energized. Said sensor means also comprises two mutually movable elements, of which one is permanently associated with the shell of the filter in which the water collects, and which is disposable, whereas the other is positioned inside a casing which contains said microprocessor and said withdrawal device, is removably connected to said shell, and is permanently associated with the vehicle.
For further details reference should be made to the text of the application cited in the introduction.
A problem which has been encountered in using the aforedescribed unit derives from the fact that the sensor means may sometimes not intervene due to its two component elements being unable to move relative to one another, and the difficulties resulting therefrom. Investigations have shown that said lack of intervention is mainly due to at least one of the following reasons.
Materials such as impurities, dirt or adhesive lumps can deposit on the element permanently associated with the vehicle, to hinder sliding of the element associated with the filter, even when this is new and clean.
In addition, as one of the two elements is replaced when the filter is replaced, dimensional inaccuracies can occur between these elements, particularly if the used and new filters pertain to different batches or originate from different operating lines. In this case coupling inaccuracies and/or misalignments thereof can occur when the shell of the new filter is connected to said water withdrawal device.
The main object of the present invention is to obviate the aforesaid problem within the context of a simple, rational, reliable and economical construction.
Said object is attained by virtue of the characteristics indicated in the claims.
In attaining said object, according to the invention said sensor means of the known unit cited in the introduction is made to consist of a differential water level reading and monitoring system comprising two measurement members, each sensitive to a level between the maximum predetermined level and the depth of said accumulation chamber, said two measurement members being connected to the unit microprocessor such that, with the vehicle engine at rest and the relative electrical system live, it energizes said withdrawal device in response to the signal received from one or other of said two members.
Moreover, apart from the respective external electric cabling, and as will be apparent hereinafter, the constituent elements of said two measurement members are advantageously permanently positioned in the lower part of the accumulation chamber of the disposable filter.
Finally, means described hereinafter are interposed between said differential reading and monitoring system and that part of the bleed unit permanently associated with the visual indicator, to verify the compatibility between the filter and the bleed unit. By virtue of the aforegoing, all the objects of the invention are attained.
In this respect, the danger of non-intervention of the sensor means is reduced to a minimum in that on the one hand the activation signal for the bleeding stage is generated even if the reading member is disabled by the presence of excessive deposits of foreign material, and on the other hand a filter having characteristics different from those required by the bleed unit cannot be mounted.
The constructional and operational characteristics and merits of the invention will be apparent from the ensuing detailed description, given with reference to the figures of the accompanying drawings, which show two preferred embodiments thereof by way of non-limiting example.